In a dye diffusion transfer recording system, a heat-sensitive transfer sheet containing dyes is superposed on a heat-sensitive transfer image-receiving sheet (hereinafter also referred to as an image-receiving sheet), and then the heat-sensitive transfer sheet is heated by a thermal head whose exothermic action is controlled by electric signals, in order to transfer the dyes contained in the heat-sensitive transfer sheet to the image-receiving sheet, thereby recording an image information. Three colors: cyan, magenta, and yellow are used for recording a color image by overlapping one color to other, thereby enabling transferring and recording a color image having continuous gradation for color densities.
In a recording system such a dye diffusion transfer process, it has been known that it is important to impart high heat insulating property to the heat-sensitive transfer image-receiving sheet in order to obtain favorable images.
Thus, for imparting heat insulating property to the heat-sensitive transfer image-receiving sheet, used may be a composite support having a microvoid-containing biaxially oriented polyolefin film as a support for the heat-sensitive transfer image-receiving sheet. However, by this method, because of relaxation of the residual stress at the time of stretching by the heat during printing or coating of a receptor layer, the heat-sensitive transfer image-receiving sheet shrinks, causing crinkling and curling.
Aside from this, proposed was installation of a heat insulation layer containing hollow polymer particles for imparting heat insulating property to the heat-sensitive transfer image-receiving sheet (see, e.g., Japanese Patents No. 2541796 and No. 3226167, JP-A-5-8572 (“JP-A” means unexamined published Japanese patent application) and JP-A-2006-88691). However, such a method is not necessarily satisfactory because the following problems have emerged: it is difficult to obtain a uniform and smooth heat-sensitive transfer image-receiving sheet, there arise improper transfer of images, white spots, surface irregularity and protective-layer adhesion failure, the production process is complicated and disadvantageous from the viewpoint of productivity. Further, such a method brings in a new problem that the glossiness of a solid black image deteriorates.
On the other hand, when a paper support is used as a support of the heat-sensitive transfer image-receiving sheet and a hollow particle layer is provided on the side thereof opposite to the side having a receptor layer, concavity-and-convexity (surface roughness), i.e., relief (image level difference) occurs on the printed image, and thus formation of a high heat-resistance particle layer between the support and the hollow particle layer is proposed (see JP-A-2005-96206). However, the relief occurs also when the image-receiving sheet has a heat-insulating layer containing hollow polymer particles on the receptor layer side, and there is a need for means for solving the problems.